Devices are known that facilitate manual hammering of staples into adjacent bone portions, such as is described in U.S. Pat. No. 4,263,903. U.S. Pat. No. 4,414,967 filed June 22, 1981, teaches the use of a stapler that rapidly and reproducibly imparts a controlled amount of energy to propel a staple into bone portions and which provides many advantages over devices of the type described in U.S. Pat. No. 4,263,903. The teachings in that application, however, were based on tests with a commercially available manually actuatable staple gun (i.e., the Model T-50 Staple Gun Tacker manufactured by Arrow Manufacturing Co.) that is impractical for surgical use.
U.S. Patent Application Ser. No. 508,588, filed June 28, 1983 described the same bone stapling device described in this application which has numerous novel design features which facilitate driving staples into bone portions during surgery. Generally, the bone stapler described in both that application and this application is a stapler of the type adapted for use with generally U-shaped staples each comprising two generally parallel leg portions projecting in the same direction from opposite ends of a central portion. The stapler comprises a housing having a passageway extending from an inlet opening to an outlet opening, which passageway is adapted to guide a single staple moved from the inlet to the outlet opening with distal ends of the leg portions of the staple leading. Means are provided for biasing a stack of staples into the inlet opening, together with a driver having an end portion adapted to engage the central portion of such a staple. The driver is mounted on the housing for sliding movement between a load position spaced from the inlet opening to afford movement of one of the staples into the passageway, along the passageway with the end portion of the driver pushing the staple, and to an eject position at which the end portion of the driver pushes the staple out the outlet opening and at which eject position the driver is stopped. Also drive means adapted to be manually activatable are provided for rapidly and forcefully propelling the driver along the passageway from its load position to its eject position to move a staple from the inlet opening to the outlet opening and drive the staple into portions of bone adjacent the outlet opening.
The novel features claimed in the above mentioned application that singly or collectively particularly adapt the stapler for driving staples into bone portions during surgery include:
(1) A compressed air activated drive means which ensures efficient operation of the stapler while not discharging any air used to operate the stapler adjacent the area at which the staples are applied to thereby restrict contamination of that area. This drive means comprises an air cylinder assembly including a cylinder having first and second ends with a portion of the driver opposite its end portion that engages a staple extending into the second end of the cylinder, which cylinder is partially defined by an inner surface of the housing around and aligned with the driver; and a piston within the cylinder fixed to the driver and in slidable sealing engagement with the inner surface. The piston is movable along the inner surface from a first position adjacent its first end at which it is positioned when the driver is in its load position to a second position adjacent the second end of the cylinder at which it is positioned when the driver is in its eject position. Also included is a valve assembly comprising the housing having a bore and having an inlet port and first and second outlet ports communicating with the bore; and an activator manually movable from a blocking position to which the actuator is biased at which the actuator closes the inlet port and connects the outlet ports, and an activate position connecting the inlet and first outlet ports and closing the second outlet port. The housing has an outlet passageway communicating with the cylinder adjacent its second end and communicating with the second outlet port, which outlet passageway is adapted to be coupled to a hose leading to air at atmospheric pressure remote from the stapler; has an inlet passageway coupled to the inlet port and adapted to be coupled to a source of air under greater than atmospheric pressure, and has a transfer passageway coupled between the first outlet port and communicating with the cylinder adjacent its first end. Thus, when the drive means is activated by moving the actuator to its activate position, air under greater than atmospheric pressure will flow through the inlet and first outlet ports and the transfer passageway to the first end of the cylinder. As the piston starts to move from its first toward its second position under the influence of the high pressure air, air between the piston and the second end of the cylinder will flow out the outlet passageway and through the bore. When the actuator is subsequently returned to its deactivated position the inlet port will be closed, and the first and second outlet ports will be connected so that the high pressure air can escape from the first end of the cylinder by the transfer passageway, the bore and the outlet passageway to the hose, and air at atmospheric pressure as needed can flow to the second end of the cylinder through the outlet passageway.
(2) Means for biasing a stack of staples into the inlet opening comprising a replaceable cartridge. The cartridge includes a case adapted to removably engage the housing and having a slot along one side surface extending generally normal to the passageway, the stack of staples within the case, and a follower on the side of the stack of staples opposite the passageway and movable within the case with the stack of staples. Means are provided for releasably retaining the case in engagement with the housing. A pusher is pivotably mounted on the housing with a distal end portion projecting through the slot and engaging the follower, and means between the pusher and the housing bias the distal end portion of the pusher toward the passageway.
(3) Structure that allows changing one part of the stapler to facilitate driving staples of different sizes. The housing and driver both comprise first and second parts. The first part of the housing defines the inlet and outlet openings and carries the means for biasing, and the second part of the housing carries the drive means. Manually actuated engagement means are provided for releasably engaging the first and second parts of the housing and driver to afford using different first parts, each adapted for staples of a different size, with the second parts.
(4) Pointed projections projecting outwardly of the housing and flanking the outlet opening which are adapted to help position and stabilize portions of bone to be joined in the same plane before the staple is driven.
(5) Means for releasably latching the driver in its load position which help ensure that a user cannot unintentionally fire a staple. This means comprises latch means adapted for automatic engagement between the housing and the driver when the driver returns to its load position from its eject position; and a manually activatable button means or botton mounted on the housing for movement from an outer position to which it is biased affording engagement of the latch means, to an inner position engaged with and releasing the latch means to afford movement of the driver to its eject position.